This reduces the number of third party dependencies for Windows builds. WinHttp is quite a nice straight forward API so doesn't involve too much extra code.
* Reduce code duplication in src\openrct2\interface\Window.cpp
`window_resize_gui_scenario_editor` was a subset of `window_resize_gui`
* Reduce code duplication in src\openrct2\network\Twitch.cpp
Both `GetFollowers()` and `GetMessage()` were very similar
* Reduce code duplication in src/openrct2/world/SmallScenery.cpp
`map_place_non_scenery_clear_func` and `map_place_scenery_clear_func` did basically the same thing, with a single branch difference
* Reduce code duplication in src/openrct2-ui/windows/TopToolbar.cpp
Make `top_toolbar_tool_update_scenery_clear` call `top_toolbar_tool_update_land_paint` and then do the additional differing calculation it did.
Clang-format sees the text behind `#pragma region` as code and formats it. Instead of stating the copyright and date there, it's now in the comment block right below it. The text "Copyright" is left in the `#pragma region` line, as clang-format sees it as a single identifier.
I took the opportunity to normalize the dates, and add the copyright notice to the source files where it was missing them (except for third-party and the generated resources.h file).
